HARROWS FOR DRY-FARMING 311 



thinned effectively. At otlier times it may be observed 

 in the spring that the rains and winds have led to 

 the formation of a crust over the soil, which must be 

 broken to let the plants have full freedom of growth 

 and development. This is accomplished by slanting 



Fig. 80. Spring tooth harrow. 



the harrow teeth backward, and the crust may then 

 be broken without serious injury to the plants. The 

 smoothing harrow is a very useful implement on the 

 dry-farm. For following the plow, however, a more 

 useful imj^lement is the disk harrow, which is a com- 

 paratively recent invention. It consists of a series of 

 disks which may be set at various angles with the line 

 of traction and thus be made to turn over the soil while 

 at the same time pulverizing it. (See Fig. 81.) The 

 best dry-farm practice is to plow in the fall and let the 

 soil lie in the rough during the winter months. In the 



